With the development of technology, mobile phones, digital cameras, tablet PCs, notebook computers and other portable electronic devices have become essential equipments for human life. To effectively avoid internal data of the personal portable electronic devices being stolen, all kinds of protection methods are provided. For example, password verification, voiceprint recognition or fingerprint recognition and so on, wherein optic fingerprint recognition is widely used. However, since a light source of a current optic fingerprint sensor has to stay on, in order to generate fingerprint images on an image sensing module, high power consumption occurs for long-time use. In addition, continuously or intermittently lighting of the light source affects sensation of users.